The PR wired in a detached watcher that respawns manual profile gateways
after they exit. Pair that with a SIGUSR1 graceful drain (same path
systemd/launchd use) so in-flight agent runs finish instead of getting
SIGTERM'd. Fall back to SIGTERM if SIGUSR1 isn't wired or the gateway
doesn't exit within the drain budget — the watcher sees the exit and
relaunches either way.
Tested end-to-end against an orphaned gateway: graceful drain exits in
0.5s and the watcher fires the relaunch command.
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